It is possible to make an applet automatically marked in GeoGebra, which generates random straight lines and lets you enter the function regulation of these. It is explained in the following guidance.

How to do

1. Show axes and grid (right click on the drawing pad and select axes / grid).
2. In the input field, type the following

   a = Random Medium[-5,5]

3. In the input field, type again following

   b = Random Medium[-5,5]

4. In the input field, type the following

   a * x   b

5. Now you have created a function f(x) with a random- and b-values.
6. Right-click the line of f(x) and select Display Name.
7. Insert a text on the drawing board using the. -button.
8. Write “Well done!” in the edit box.
   
9. Press OK.
10. Press -button.
11. Press text “Well done!” on the drawing pad.
12. Press the small arrow, which is the sign block.
13. This will give you back access to additional features.
    
14. Change letter size to very large.
15. Now you need to add a new function g(x). (You do this in the input field. This function is later hidden and controlled by button “Insert Text Field”.) Write in the input field:
    g(x)= 0
16. Right-click the line of g(x) and select Display Name.
17. Insert text field by pressing -button and then press the drawing pad.
    
18. At the Caption you write “Skriv forskrift for f f(x)=”.
19. Choose g(x)= 0 for “Hooked object“.
20. Press “Apply”.
21. Right click on the text “Well done!” on the drawing pad and select properties.
22. Under the tab “Advanced” , under “Condition to show object” write f == g
    
23. It is automatically changed to f ≟ g
24. Press the junction to close the properties.
25. Indsæt en knap vha. -button (in the toolbar).
    
26. Write “NEW FEATURE” in the Caption field.
27. Type the following in GeoGebra script field:

    Select the Active Display[1]
    OpdaterKonstruktionen[]

28. Press OK.
29. Press -button.
30. Remove the algebra window (possibly. under the view menu or by pressing the junction at algebra)
31. Press “NEW FEATURE” and write operation regulation of the straight line in the text box.

See and download the assignment here:

www.geogebratube.org/material/show/id/44829

Change the color, thickness m.m. for graphs

1. Press -button.
2. Pressure on the graph(line) for f(x).
3. Press the small arrow, which is the sign block.
4. This will give you back access to additional features.
   
5. Change the color, such as blue.
6. Make the line dotted.

Change the color, font size m.m. the button.

1. Press -button.
2. Right-click the button.
3. Choose properties.
4. During the tabs Text, Color and Style can change most things.
5. Be aware of, to see Colour choosing color, respectively. background color and foreground color by pressing: